Especially small children, who cannot watch out and have small fingers, run the risk of accidentally inserting their fingers into the chink of an elevator door, i.e. into the gap between two door panels sliding with respect to each other or between a door panel and the door frame. The width of such a chink or gap is typically 5–6 mm, and a smaller gap is difficult to achieve because the tolerances required in manufacture and operation do not allow it.
To solve this problem, light cells and other electric sensors have been used. A drawback with these is that they involve delays, as a result of which the door can not stop in time. Moreover, in a critical situation they may fail to function reliably. In particular, the large weight of glass doors involves a special risk as they continue moving by virtue of their mass even if the sensors should have responded. Sensors are also subject to vandalism as they are exposed to sight and susceptible to malicious damage or interference. Therefore, they also involve significant maintenance and repair costs.
A prior-art solution is also presented in patent specification U.S. Pat. No. 5,794,745. The finger guard according to this patent comprises a brush-like strip attached to the edge of the door frame on the side facing toward the door opening, which strip, being mounted in an obliquely outward directed orientation against the door surface, covers and closes the gap between the door and the frame at least from direct sight. This solution does not prevent fingers from getting into the gap but only arouses the person to quickly draw his/her hand away if the fingers touch the brush. Another disadvantage in this solution is surface-mounted installation and visibility of the structure, which means that it is susceptible to damage and vandalism. Moreover, the structure reduces the size of the door opening especially if the doors can move to a position completely outside or flush with the door opening delimited by the frame. Besides, this structure is difficult to apply between two door panels because in that case it directly reduces the size of the door opening and forms edges or flanges that may catch elevator passengers or objects carried along.